Updates of Semileptonic Results for ICHEP08 2008

This web page contains the results for ICHEP 2008.
The changes of this update with respect to the the End of Year 2007 update are described here. A new common parameter file is adopted. Moreover,
charge coniugated final states are always included.
We thank U. Aglietti, I. Bigi, G. Ferrera, P. Gambino, E. Gardi, P. Giordano, Z. Ligeti, M. Neubert, G. Ricciardi, N. Uraltsev for useful discussions and providing the theoretical codes.
f1vcb_rho2.html

Measurement of |Vcb| F(1) in B0 -> D*-lnu

The following average is based on a global four-dimensional fit of
|Vcb|F(1), r2,
R1 and R2 to the experiments listed.
This table and the plots are based on the global fit values of
R1 and R2.
The values reported for each experiment have been rescaled to
R1=1.369±0.064 and R2=0.846±0.038
obtained from the fit. The errors contain both the common and the experiment
dependent systematic uncertainties. All available experiments have been included in
the average.

Exclusive Branching Fraction: B0 -> D*-lnu

This is a list of branching fractions from individual experiments
corrected for R1 and R2.
The average is based on the integral over
the differential rate
dG/dw
based on the four-dimensional fit of |Vcb|F(1),
r2, R1
and R2 (see above).
The errors include both the common
and experiment dependent systematics. The BaBar tagged result only measures the
branching fractions and is averaged independently with the output of the first
average.

Exclusive Branching Fraction: B- -> D1(D*-pi-)lnu

We report the average for the product of branching fractions of B- ->
D1(D*-pi)lnu and D1 -> D*+pi-. Apart for
the CLEO,BELLE and BABAR results, the other measurements are for the final state
D1(D*-pi-)X. We assume that no particle is left in the X
system.

Exclusive Branching Fraction: B- -> D2(D*-pi-)lnu

We report the average for the product of branching fractions of B- ->
D2(D*-pi)lnu and D2 -> D*+pi-. Apart for
the CLEO, BELLE and BABAR results, the other measurements are for the final state
D2(D*-pi-)X. We assume that no particle is left in the X
system.

Exclusive Branching Fraction: B+ -> D*0lnu

The branching fractions are obtained from the integral over the measured
differential decay rates. The BaBar tagged result is obtained
by a 1-d fit to the missing mass in fully reconstructed events. The average BF is obtained from a one-dimensional fit of the measurements listed.

Measurement of |Vcb|G(1) in B -> Dlnu

The table and plots give the results of two-dimensional fits to |Vcb|G(1)| and rho2 for different experiments, using the form factor parameterization of Caprini, Lellouch, and Neubert, Nucl.Phys. B530 (1998) 153-181 [arXiv:hep-ph/9712417v1].
nada

Exclusive Branching Fraction: B0 -> D-lnu

The branching fractions are obtained from the integral over the measured differential decay rates. The BaBar result is obtained by a 1-d fit to the missing mass in fully reconstructed events. The average BF is obtained from a one-dimensional fit of the measurements listed.

Exclusive Branching Fraction: B- -> D0lnu

The branching fractions are obtained from the integral over the
measured differential decay rates. The BaBar result is obtained by a 1-d fit to the missing mass in fully reconstructed events.
The average BF is obtained from a one-dimensional fit of the measurements listed.

The branching fractions are obtained from the integral over the measured differential decay rates. The BaBar tagged result is obtained
by a 1-d fit to the missing mass in fully reconstructed events. The average BF is obtained from a one-dimensional fit of the measurements listed.

Inclusive |Vcb| from global fits

Global fits to the moments of inclusive distributions in B ->
Xc l nu (lepton energy and hadron mass) and B ->
Xs gamma (photon energy) transitions are performed in the
framework of the Heavy Quark Expansion (HQE), using the calculations in
the kinetic mass scheme:

The errors quoted are the results of the MINUIT fit, where the
covariance matrix includes experimental and estimated theoretical
uncertainties. On |Vcb| there are additional uncertainties:
The second error corresponds to the uncertainty in the B lifetime, and
the third error is an additional theoretical uncertainty of 1.4%
related to the conversion of the semileptonic branching ratio into
|Vcb|.
The b quark mass and mupi2 also also translated
in other schemes as necessary input parameters for the extraction of |Vub|
from inclusive b->ulnu decays.

Translation to other schemes of the parameters from the B -> Xc l nu & B -> Xs gamma fit

Scheme

mb (GeV)

mupi2
(GeV2)

Comments

SF

4.631 +0.041 -0.035 GeV

0.272 +0.056 -0.076 GeV

Using code from M. Neubert. The total error, for both parameters, is due to the contribution of the error due to the ellipse and the one due to scale variation for alphas.

MSbar

4.243 +- 0.042 GeV

E. Gardi

1S

4.70 +/- 0.03 GeV

Inclusive Vub average for ICHEP08

|Vub| from inclusive semileptonic B decays

The results in this section are determined by comparing the measured partial branching fractions in selected regions of phase-space to theoretical calculations of the corresponding rates, which depends on |Vub|. The following theoretical calculations are used to extract |Vub|:

In the |Vub| averages only measurements for which the correlation is known are considered. They are either independent measurements or correlated measurements for which the correlation among the analyses is available (eg the BaBar B-Reco analyses). If the analyses are correlated but the correlation is not known, the analysis with the smallest error is considered.

No attempt is made to average values for |Vub| from the different theoretical models, but the results are presented independently per each scheme.

The input files for the average are linked in the tables with the averages. To summarize briefly, all theoretical uncertainties are considered to be correlated, as are the uncertainties on the modeling of b -> clnu and b -> ulnu decays. Experimental uncertainties (particle identification, reconstruction efficiencies, etc.) are taken as correlated amongst measurements from the same experiment, but not correlated across experiments.

The errors in the tables are experimental (statistical and
systematic) and external (theoretical and HQ parameter uncertainties).
The average B lifetime used is 1.573 ps. Final state radiation is included in all the measurements.

where the fractions correspond to the statistical error (stat), the experimental systematics (exp), the modeling, e.g. branching fractions for exclusive decays, of b -> c l nu and b -> u l nu decays (b2c model and b2u model, respectively), the HQE parameters mb and mupi2 (HQE param), the functional form of the SF (ie the variation from the exponential to the Gaussian form of the SF, SF func), the subleading shape functions (sub SF), the variation of the matching scales (matching), and the Weak Annihilation (WA). No uncertainty is assigned for possible duality violations. The quoted experimental error in the table above corresponds to the statistical, experimental systematic and the b -> c l nu and b -> u l nu modeling errors. The other uncertainties contribute to the theoretical error.

where the fractions correspond to the statistical error (stat), the experimental systematics (exp), the modeling, e.g. branching fractions for exclusive decays, of the b -> c l nu and b -> u l nu decays (b2c model and b2u model, respectively), the effect of the alphas uncertainty on R_CUT (alpha_s R_CUT), the effect of the uncertainty on mb on the prediction of the event fraction and the total rate (mb), the Weak Annihilation (WA) and from the change and variation of scale of the matching scheme (DGE theory). The quoted experimental error in the table above corresponds to the statistical, experimental systematic and the b -> c l and b -> u l nu modeling errors. The other uncertainties contribute to the theoretical error.

where the fractions correspond to the statistical error (stat), the experimental systematics (exp), the modeling, e.g. branching fractions for exclusive decays, of the b -> c l nu and b -> u l nu decays (b2c model and b2u model, respectively),
the value of alpha_s, mb and other non-perturbative parameters (par.),
higher order perturbative and non-perturbative corrections (pert.),
the modelling of the q2 tail and choice of the scale q2* (q2*),
the WA matrix element (WA),
the functional form of the distribution functions (ff).

where the fractions correspond to the statistical error (stat), the experimental systematics (exp), the modeling, e.g. branching fractions for exclusive decays, of the b -> c l nu and b -> u l nu decays (b2c model and b2u model, respectively), the effect of the alphas uncertainty (alpha_s), the effect of the uncertainty on Vcb (Vcb), on the b-quark mass in the MS scheme (mb), on the c-quark mass in the MS scheme (mc), on the semileptonic BF (BF) and on the model (model). The quoted experimental error in the table above corresponds to the statistical, experimental systematic and the b -> c l and b -> u l nu modeling errors. The other uncertainties contribute to the theoretical error.

where the fractions correspond to the statistical error (stat), the experimental systematics (exp), the modeling, e.g. branching fractions for exclusive decays, of b -> c l nu and b -> u l nu decays (b2c model and b2u model, respectively), the residual shape function effects (Strf), the higher order terms in the alphas expansion (Pert), the uncertainty on the b-quark mass (Sf), and the third order terms in the OPE expansion(H.O.). No uncertainty is assigned for possible duality violations.

Several years ago, M. Neubert (Phys. Rev. D49, 4623 (1994) ) suggested that |Vub| could be extracted by combining weighted integrals over the photon spectrum in B->Xs gamma decays with integrals over the lepton momentum spectrum near the kinematic endpoint in inclusive B->Xulnu decays decays. The underlying assumption is that the QCD interactions affecting these two processes are the same to leading order, and therefore ratios of decay rates for the two processes have significantly lower sensitivity to the choice of the shape-functions parameterization.
So far, there are two BABAR measurements based on this suggestion to extract |Vub| from charmless B-meson decays from inclusive distributions for different regions of phase space.
BABAR measured |Vub| in inclusive decays using the prescription of Leibovich, Low, and Rothstein (LLR), Phys.Rev.D62:014010,2000 [arXiv:hep-ph/0001028v2], and Phys.Lett.B486:86-91,2000 [arXiv:hep-ph/0005124v1], that extracts |Vub| with reduced model dependence by combining data of the hadronic mass spectrum from B->Xulnu decays with that of the photon energy spectrum from B->Xs gamma decays (Phys.Rev. D72 (2005) 052004 [arXiv:hep-ex/0508004v2]).
Using BABAR measurements of the lepton momentum spectrum near the kinematic endpoint, Phys.Rev. D73 (2006) 012006 [arXiv:hep-ex/0509040v2], two different theoretical prescriptions were tried to extract |Vub|, Phys.Rev.D76:114003,2007 [arXiv:hep-ph/0702072], namely LLR (Phys.Rev. D61 (2000) 053006 [arXiv:hep-ph/9909404v2]]) and LNP, a calculation by Lange, Neubert and Paz (JHEP 0510 (2005) 084 [arXiv:hep-ph/0508178v2] and JHEP 0601 (2006) 104 [arXiv:hep-ph/0511098v1]).
In the following, we provide a comparison of the results of the different |Vub| extractions.

The errors on |Vub| are experimental and theoretical, respectively, for the first three results and experimental on B->Xulnu, experimental on B->Xsgamma, theoretical and due to |Vts| for the last two measurments.

Exclusive |Vub| determination

The partial BF quoted above along with theoretical calculations of the form factor normalization can be used to determine |Vub|; a few recent calculations are shown below. Note that the FNAL04 and HPQCD unquenched LQCD calculations are not entirely independent, and we do not use their quenched results as they are superseded by their unquenched results. The Ball-Zwicky calculation is based on light-cone sum rules. At this time we do not attempt to average the |Vub| results or select a best value.